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winter water

delfin 700

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If you stop the valve from working you could ruin the boiler especially it the water inside gets frozen. If the heating is on it should be Ok. You can also turn the supply off too the pump which will stop it emptying the tank.
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As per that other linked-to thread, it's pretty usual practise for folk just use a peg, bulldog clip, R clip or tie it up/closed...

I used an R clip on our older *plunger type valve, as ours once dropped the boilers' water whilst travelling ( *although I've read on here that later valves were harder to override/"jam"?)


I think our valve was supposed to "dump" at around +4-5 degrees C? (and needed to be above 8 degrees to reset again?), so it opened well above the point the boiler was likely to freeze up.

(..a pain in the backside when trying to take on water before setting out at this time of



Obviously when pitched up in "proper" freezing conditions, you'd probably have additional heat of sorts running in the van, in which case you could probably let the valve do it's things?...


(..although whenever we were just away for a night or two during really cold spells, as we would've probably been somewhere with some facilities anyway, we tended to leave the van fully drained and just took a couple of containers)


Edit- delfin I've just noticed you have already asked this question and it had already been answered :-S



(sorry Derek, I crossed your post)

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delfin 700 - 2016-12-08 7:19 PM


i have a burstner delfin 700 and we went out in it for a few days with frost outside it emptyed the fresh water via the safety valve does anyone know how we can get over the water dropping over a frost please


I’m unsure why you’ve revisited this, as I thought it had been well covered when you enquired about it on 30 November 2016.




QFour advises that "You can also turn the supply off to the pump which will stop it emptying the tank”, but that will only apply if the water-pump is a pressure-sensitive diaphragm type.


If a ‘submersible’ water-pump has been fitted (where the pump is under water in the motorhome’s fresh-water tank) when the Truma safety/drain valve opens and water begins to drain from the heater through the valve, there’s a good chance this water-flow will provoke siphoning from the fresh-water tank, with the water in the tank passing through the pump and non-return valve and out through the safety/drain valve. If siphoning begins, even when the heater has finished draining, siphoning from the fresh-water tank will continue until the tank is empty.


I recall the 'tank-siphoning' risk coming up years ago (possibly in MMM’s “Interchange” columns) and that Burstner motorhomes were involved. Burstner were installing diaphragm or submersible water-pumps according to the motorhome model and those with submersible pumps were emptying their fresh-water tanks in cold weather when the Truma safety/drain valve opened despite the water-pump being switched off when this happened. Burstner were asked to comment and advised that this could happen and - other than leaving the Trumatic C-Series heater switched on - there was no way to guard against it.


When a Truma Elasi electrically-operated safety/drain valve is fitted there are two options to prevent it opening in cold weather. One is to ‘jam’ it in its closed position and the other is to have the Trumatic C-Series heater switched on. In the latter case, the heater does not need to be actually heating water or air - it just needs to be switched on with the ‘operating normally’ green light illuminated continuously on the heater’s control-panel.

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Been concerned about this with our van, - We have Truma combi 4 e in the garage.


If the dump valve (which is a manual reset affair) does trigger, it does empty the boiler tank contents onto the ground however it doesn't seem to drain the rest of the system even if the electrics including the pump are on, - there is clearly something to stop this happening. I did wonder, so I tried this as an experiment.


I have had the situation where it is so cold that the thing dumps and will not re-set (or I dumped it) and then am trying to re-fill everything and get it going again and cannot re-set.


The Truma instruction's I have cover this scenario, - all I need to do is put the heating on, - heats the van and the garage but without water heating, - when it's warm enough it does allow me to re-set the valve and life is good, I switch on water heating - as long as we keep a minimum of heat to prevent it happening again.


Since the boiler is in the garage, it warms up nicely and tends to stay pretty warm.


We where warned - This is about £3000 worth of kit, and the last thing I want to happen is to "wedge" the valve and find I have inadvertently caused mega damage after forgetting about the thing.

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The critical thing is not the water-pump being switched on - it’s the type of water pump that the motorhome manufacturer has installed and how that pump is triggered.


When a motorhome has a ’submersible’ pump, it is normally triggered by microswitches on the hot-and-cold water outlets. The pump can be switched on at the motorhome’s control-panel, but it won’t start pumping water until one of the water-outlets (eg. a tap or shower) is turned on. Consequently, if a Truma safety/drain valve opens, even if a submersible pump has been turned on at the control-panel, the pump itself will not run. As I’ve mentioned above, there is a potential risk that water will siphon from the fresh-water tank despite a submersible pump not running, but in many (most?) cases siphoning won’t occur and just the Truma heater’s water-tank will empty.


When a motorhome’s water-pump is triggered by a pressure-sensitive switch or the pump itself is pressure-sensitive, if the pump is switched on at the control-panel and the Truma drain valve opens this will cause the pressure in the water system to drop, triggering the pump that will then start to empty the fresh-water tank.


(There is a variant where a pressure-sensitive diaphragm pump is triggered by water-outlet microswitches. Ignoring the additional complexity, this is probably the best of both worlds as the pump won’t run unless a water-outlet is opened and the system should not siphon.)


Trumatic C-Series and “Combi” appliances are intended to recirculate warmed air within the motorhome’s living space. Truma’s installation instructions recommend that the heater should be roughly in the centre of the habitation area, be provided with plenty of ventilation and that the air trunks be of approximately equal length. Putting the heater in a motorhome’s garage means that it’s likely to be recirculating warmed air inefficiently (or not recirculating it at all) and that the air trunks will be a mixture of long and short. There’s no doubt that an ‘in garage’ heater will warm up the garage but, unless a favourite pet is living there, why would one want a hot garage?

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Thanks Derek - makes sense.


Our Truma is possibly a little lower than the inboard fresh tank so in theory you are indeed correct, water could flow via a syphon action I suppose.


My thoughts are of a concern with the pressure variety of water opening, - If the pressure drops for any reason, eg a leak, the pump might come on and 90ltrs of water flowing into the van might not do it much good !!. Think I would rather have a system that is essentially off until a micro switch is triggered rather than one that is on and is dependant on water pressure being maintained. In a vehicle environment where everything flexes including pipe joints can see the risk if we went out with the pump on.


As to heating the garage, good point although the pipes run up from the garage up along the sides of our beds which is above, and when it's -3 outside as it was last time out, very toasty. I would imagine it's easier to insulate the entire skin of the van including the garage rather than try and seal the van from the garage, - some of the under bed spaces run right through, Puts the Truma in a space where plenty of air is available and it can breath - and for our fairly small van it works a treat, very impressed as to how good it is, -We monitored the temperature, a comfy 19c throughout, dropped to 18C at one point - Coldest place was the cab.


Checked the price of new Truma,s Combi - £3000 is a little overstated, more like £1500 but would take some effort to change over.

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delfin 700 - 2016-12-09 10:05 PM


many thanks to everyone how as helped me on the value dumping they have all been very helpful




It makes far more sense to post replies of thanks on the relevant thread. And it keeps the forum tidier, I'll delete your two irrelevant posts.



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